Process for rendering a material fire retardant

ABSTRACT

A fire retardant material is formed by intimately associating the unexpanded form of perlite in association with a permeable mass of silica glass, said association is formed by permeating said perlite into said mass of glass. Preferedly the composition comprises particles of unexpanded perlite less than 100 mesh and preferably no larger than 200 mesh and the permeable glass comprises a glass fiber mat. The fire retardant material can be formed as a unified body capable of being applied onto other structural components or alternately, it can be intimately bonded to the surface of structural components as a veneer layer. Upon exposure to combustion temperatures the perlite expands from its unexpanded form to its expanded form at or near the deformation point of the glass mat followed by reaction of the perlite and the glass to form a flame-impenetrable ceramic.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 343,880, filedJan. 29, 1982, now U.S. Pat. No. 4,443,258, which is acontinuation-in-part of my application entitled, FIRE RETARDANTMATERIALS, Ser. No. 214,220, filed Dec. 8, 1980, abandoned the entiredisclosure of which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

This invention is directed to a fire retardant material which utilizes apermeable mass of glass permeated with the unexpanded form of perlite.Upon exposure to combustion temperatures the heat expandable materialexpands followed by reaction of this material with the glass to form aceramic.

It has been the goal of certain industries to produce structuralmaterials such as roofing compositions and insulation which are capableof retarding the spread of flame in case of catastrophic fire in abuilding. To this end, certain specifications have been set up asguidelines in evaluating these materials for their flame retardantproperties. Underwriters' Laboratory tests set forth specific parametersin tests of materials for their flame retardant abilities. UL test 790includes Fire Brand tests as part of these parameters. The Fire Brandtests are rated such as Fire Brand A, Fire Brand B and Fire Brand C. Thecriteria of the A and B tests are very stringent and most products failto meet them.

Certain inorganic compositions which themselves are not combustible havebeen incorporated into both roofing materials and insulation. Use ofthese materials, however, is governed by many factors. They, of course,must be available in large quantities and at an economical price. Bytheir very nature, however, they tend to be extremely dense and thusimpractical to use by themselves because of the structures needed tosupport their weight. Further, solid bodies of these inorganic materialstend to be extremely brittle. Although they have considerablecompression strength, their sheer strength is extremely poor. For thesereasons, if these materials are used it has been found necessary tonormally incorporate them into matrices of other materials.

The above noted fire resistant materials include materials such asclays, silicas, glasses and minerals such as asbestos, expanded perliteand expanded vermiculite. Asbestos is not suited for most uses becauseof the health hazard associated with fine fibers within the lungs. Claysand the like are so extremely dense that their use is limited to certaininstallations, such as tile roofs, floor tiles and the like. Except forbrick walls, the use of clays cannot be extended to walls. Expandedperlite and vermiculite have no structural strength when used neat, andthus cannot be used without other supporting materials.

Expanded perlite and vermiculite, however, have been found to be usefulas fillers in insulation and to reduce the density of certainaggregates. In this regard other structural components are used toimpart structural strength to the insulation or aggregate and theexpanded perlite or vermiculite is added to this to form dead areaswithin the matrix of the structural material.

When the expanded perlite or vermiculite is used as a filler ininsulation they impart very good fire retardant properties to thematerial. However, the matrix material which is used to support them inthe past has either been extremely dense inorganic composition or hasbeen a material which is susceptible to combustion, such as organicresins and the like. Examples of use of expanded perlite and vermiculitewithin matrices are found in U.S. Pat. Nos. 3,987,018; 4,011,194;2,634,208 and 2,884,380. In these notes U.S. patents, which use anexpanded composition in an organic matrix, the products describedtherein will only be useful at temperatures below that of the combustionpoint of the matrix material.

In a fire, the presence of an insulating material will help slow theheat spread from one area to an adjoining area. In addition to heatspread, it is also desirable to inhibit gas movement to seal off thefire. Thus, in addition to serving as an insulating material, materialswhich are effectively impenetrable to gas movement assist in preventingflame spread by inhibiting oxygen availability to the source of thecombustion. Those insulating materials which are either porous or whichhave a combustible matrix are therefore of little utility in inhibitingmovement of oxygen to the source of the flame.

In view of the above discussion it is evident that there exists a needfor materials which are capable of serving as insulators and flamespread preventers or inhibitors. Certain presently used constructionmaterials, such as concrete or metals, can serve to meet this need.However, in certain structures their use is precluded by either theirweight, their cost, or architectural considerations. In these types ofstructures the need for efficient fire retardant materials has not yetbeen satisfied.

BRIEF SUMMARY OF THE INVENTION

It is an object of this invention to provide new and improved fireretardant materials which are capable of inhibiting the spread ofcombustion by both forming an insulative heat barrier and a gasinhibiting barrier. It is a further object of this invention to providesuch flame retardant materials which are composed of essentiallyinexpensive and readily available materials and which are adaptable to avariety of applications such as both roofing materials and in-wall andfloor insulation.

These and other objects as will become evident from the remainder ofthis application are achieved by a fire retardant material whichcomprises a quantity of a permeable mass of a silica based glass; aquantity of the unexpanded form of perlite, said quantity of saidunexpanded perlite present as a multiplicity of particles, saidparticles permeated among and associated with said permeable mass ofglass, said particles being of a size sufficiently small to be retainedin said association with said permeable mass of glass upon conversion ofsaid composition from said unexpanded form to its expanded form whensubjected to heat.

In the presently preferred form of the invention, the perlite is of amesh size less than 100 mesh and more preferably equal to or less than200 mesh and the glass is present as a glass fiber structure such as amat or fabric. The association of the perlite with the glass can beassisted by the use of a binding agent. Perferredly, the binding agentwould be an agent which would be resistant to normal ambientenvironmental stresses such as wind, water, and hot and cold expansionand contraction.

The perlite would be present in an unexpanded form in at least equalweight with the weight of the glass. However, preferredly the perlitewould be present in a percentage by weight of the total material in anamount several times greater than the amount by weight of the glass.

When used as a roofing composition preferredly a glass fiber mat havinga density greater than 0.9 lbs. per 100 sq.ft. is used and a binderwhich is essentially weather-resistant is used to maintain theassociation of the perlite with the glass fibers.

This invention utilizes certain principles and/or concepts which are setforth in the claims appended to this specification. Those skilled in theconstruction arts will realize that these principles and/or concepts arecapable of being utilized in a variety of individual materials differingfrom those used for illustrative purposes herein. For this reason thisinvention is to be construed in light of the claims and is not to beconstrued to be limited to the exact illustrated examples used herein.

DETAILED DESCRIPTION

I have found that certain essentially inorganic compositions which areheat expandable can be positioned in their unexpanded state in and amongthe individual fibers, particles, etc., of certain permeable masses ofglass and be maintained there when the material expands from itsunexpanded state to its expanded state if in fact the material is of aparticle size when it is associated with the glass in its unexpandedstate.

Further, I have found that the above noted expandable perlite, afterexpansion, while being retained in an intimate association with theglass will form a structurally stable ceramic when exposed to high heatwhich provides an inhibiting barrier for gas movement (particularlyoxygen) from one side of the ceramic to the other.

In certain applications, to assist in maintaining the unexpanded form ofthe heat expandable perlite in association with the permeable mass ofglass, binders can be added. Normally these binders would be added inorder to maintain the above noted association intact for long periods oftime during the life of the structure on which the fire retardantmaterial of the invention would be used. In certain uses of theinvention, the fire retardant material would form the outer layer on thestructure and thus a weather-resistant binder would be used inassociation with the permeable glass and the unexpanded form of the heatexpandable perlite. In other instances, a binder might be incorporatedin order to maintain the permeable glass and the unexpanded form of theheat expandable perlite in position within the interior of thestructure, such as use on walls or on ceilings and other suchinstallations. In other instances, wherein the glass and the unexpandedform of the heat expandable perlite are essentially isolated from theenvironment, a binder would not be required, but in fact portions of thestructure on which they are used would serve to insure maintenance ofthe intimate relationship between the permeable glass and the unexpandedform of the heat expandable composition.

In other uses of the invention, layers of permeable glasses, each havingthe unexpanded from of the heat expandable perlite permeated therein,would be joined together with appropriate binders. In one specificinstance, the glass itself will also serve as a binder. Thus, when watersoluble sodium silicates are used as the glass, this effect is present.

The heat expandable perlite useful in the invention is material that iscapable of expanding from its unexpanded state to its expanded state atan elevated temperature greater than 1200° F. This is a natural product,economically obtainable, which includes within its structure water as anexpanding agent.

A related material, obsidian, is generally differentiated from perliteby its lower water content. For purposes of this specification, thoseobsidians containing sufficient water such that they are heatexpandable, at or about the expansion temperature of perlite, areconsidered to be included in the classification of perlite.

For the purposes of this specification and the claims appended hereto,the word "glass" is not to be construed utilizing a strictly physicaldefinition which would include all vitreous amorphous solids and othersolids which are in fact crystalline, but on a macro scale appear to bevitreous amorphous solids. As used herein, the word "glass" is construedto include certain chemical composition limitations, limiting it tosilica based vitreous amorphous solids. As noted in the preceding, thematerial of the invention, upon exposure to sufficient heat, forms astructurally stable ceramic. The formation of the ceramic requires thepresence of both the perlite of the invention and a suitable silicabased glass.

Excluded from the scope of the word "glass" as utilized in thisspecification and the claims appended hereto, are certain materials suchas those materials noted as glass ceramics which are utilized for theproduction of certain articles, such as cooking ware and the like. Theseglass ceramics are not totally vitreous amorphous solids, but aredevitrified to at least some extent, and include nucleating agents intheir formation such that crystallization in at least a portion of theirstructure is present. Also excluded would be certain glass productshaving unusual compositions which are based upon other inorganic oxidesother than silicon oxides as their major constituent. Included in thisgroup would be materials having as their major components boric oxide,phosphoric oxide and other glass formers.

The word "glass" as used herein is further construed to exclude certainnatural and synthetically formed mineral fibers, commonly referred to asmineral wools, mineral cottons and the like. Natural fibes so definedwould include asbestos and the like. The synthetic fibers in this groupare prepared by blowing air or steam through molten rocks or slags. Theslags generally are vitreous by-products, separated from fused metalsduring melting of ores.

The glasses of the invention are therefore silica glasses. Normally, thepreferred silica glasses of the invention are generally those which areeconomical in nature. These readily available, economic silica glasseswould generally have at least about 60 percent silica content. Otheroxides would be present in varying amounts, such that the peferredsilica glasses of the invention would generally include alkali metaloxides and alkaline earth metal oxides in varying amounts, dependingupon the exact composition of the glass. Normally, these glasses alsomight contain small amounts of aluminum or boric oxides.

From an economic and performance consideration, as will be evident fromthe examples below, the preferred glass of the invention would be a sodaor potash silica glass with the glass commonly characterized as asoda-lime-silica glass being the most readily available, andeconomically preferred. Aside from the presence of silica, these glassescontain varying amounts of the oxides of aluminum, boron, sodium,potassium, calcium and magnesium. Generally, the sodium and calciumoxides form the predominant amount of the minor constituents, with themajor constituent, silica, present in percentages generally greater than60 percent.

For the purposes of simplicity of this specification, when used, exceptas otherwise noted, the word "glass" is to be construed within theconfines of the above identified limits.

The glass used in the fire retardant material of this invention isrequired to contain voids or spaces between individual amounts of massesof the glass or, in the alternative, must be soluble so that the solventcould also act as a suspending agent for positioning quantities of theunexpanded form of the perlite between individual solubilized amounts ofthe soluble glass. The glasses useful for the invention could generallybe characterized as glasses present in a divided or permeable form.

Aside from its production in sheet form, many types of glass areproduced in what can be called a divided form. These include fibers,small particles, and other similar forms.

Glass in a fibrous form is produced in great quantity as twines, matsand fabrics. The mats currently find use in roofing composition,insulations and the like, and the fabrics as support matrices forcertain polymerizable resins which together are technically calledfiberglass. Ropes or twines of glass fibers are also commonly used inchopper gun assemblies and concurrently disbursed with the individualcomponents of plural component systems to form fiberglasses and the likewithin the interiors of molds, or on the surfaces of structures and thelike. One of the most commonly used of these glass structures is knownas E-grade glass mat, and is used as a reinforcement material in theroofing industry. Glasses, of course, soften and eventually become amobile liquid over a wide temperature range. This temperature rangedepends on the chemical composition of the glass and its physical form.Finely divided fibers would be expected to initially lose theirstructural strength before thicker fibers. The E-grade mat tends tosoften between 1500° and 1600° F. and will continue to become lessviscous until the individual fibers of the mat essentially coalesce intoa monolithic mass of glass.

Other forms of glass useful in the practice of the invention are alsoproduced in great quantities. Ground glass is easily produced by thethermo-shock of rapidly cooling a mass of glass. Glass microspheres areproduced both intentionally in certain industrial processes, and asby-products of others. Certain glasses composed only of sodium andsilicates are water soluble and are noted as water glasses. These, alongwith their other alkali metal counterparts are produced in largequantities and find a variety of uses as binders, additives and thelike.

The above noted fibers, mats, fabrics, ground glass, microspheres andsoluble water glasses all have a physical property in common, in thatthere are voids between the individual fibers or solid particles, or inthe case of solutions of water glass, within the solvent itself, whereinother materials can theoretically be positioned.

I have found by using the unexpanded from of a heat expandable perlite,that I can successfully position a sufficient amount of the perlite inintimate association throughout the glass such that the composition iscapable of both expanding to its expanded form when subjected to heat toform an insulation barrier, as well as be present in an amount and bedispersed with the glass such that the perlite and the glass will reactat higher temperatures to form a ceramic composition which, in effect,forms a barrier to the propogation of the spread of flame. Theseproperties are obtainable by the use of the unexpanded form of perlite.

Generally, the perlite will initiate expansion at a temperature at orabout 1500° F. After expansion above this temperature, the perlite willbe in its expanded form and will have a plurality of voids or deadspaces within it which serve as insulative barriers to the propogationof heat through my fire retardant material. In a catastrophic fire,however, temperatures much greater than 1500° F. can be generated. At orabout 2000° F., the expanded form of the heat expandable perlite and theglass will begin to form a ceramic. Once formed, this ceramic thenserves as a physical barrier to further inhibit the spread ofcombustion.

Depending on the choice of materials, consistent with the disclosuresherein, the above noted temperatures of initiation of formation of theceramic will vary. In any event, the choice of the materials asdisclosed herein will serve to impart to my fire retardant material theabove two fire inhibiting properties; that is, both the insulatoryproperty and the formation of a ceramic barrier.

Because I initially start with the unexpanded form of heat expandableperlite, I am able to impregnate or impermeate the glass with asufficient amount of the heat expandable perlite to form the above notedceramic. If, in fact, the expanded form of perlite were initially used,the same properties could not be obtained. The expanded form of perlitecould not be present in sufficient amount to form a ceramic havingproperties of the ceramic I achieve utilizing initially the unexpandedform of this material. In order to form the ceramic having thestructural properties such that it is capable of maintaining itself as aphysical barrier at very high temperatures, i.e. generally above 2000°F., it is necessary to initially use the unexpanded from of the heatexpandable perlite.

The unexpanded form of the heat expandable perlite must further beutilized as a particle of sufficiently small size such that uponconversion to its expanded form when subjected to combustiontemperatures, it does not dislodge itself from association with theglass due to propulsion from the surface of the glass upon expansion.For the preferred embodiment below, I have found that particle size of200 mesh or smaller will expand in a manner such that their force ofexpansion will not cause them to be exploded or propelled away from theglass, whereas generally, unexpanded perlite of about 100 mesh starts todislodge itself from the glass matrix upon rapid heating.

In certain instances in using my fire retardant material, the use of abinder can augment the properties of the heat expandable perlite and theglass noted above. While the heat expandable perlite and the glass willmaintain themselves in an intimate association in normal environments,they could, when subjected to very violent environments, disassociatefrom each other. Thus, when used as the outer skin of a structure, myfire retardant material would preferredly incorporate a binder to assistin maintaining the unexpanded form of the heat expandable composition inintimate association with the permeable mass of glass.

As candidates for binders would be materials capable of being applied ina fluid state and then being converted to a tacky or solid state. Suchconversion could be based on temperature, chemical reactivity, orevaporation of a solvent. In any event, the binder should be chosen suchthat it assists in maintaining the association of the heat expandablecomposition and the glass at least at temperatures below initialcombustion temperatures of normal flammable structural materials. One ofthe binders useful in my fire retardant material in fact assists inmaintaining this association at temperatures even above such initialcombustion temperatures.

As preferred for binders would be asphalts, natural organic polymers andsynthetic organic polymers. A more preferred group of binders would be agroup consisting of asphalts, vinyl emulsions, latex emulsions,urethanes, acrylic copolymers, ureaformaldehyde, melamine, and solublealkali metal silicates. Other binders, such as organic starches,proteins and other organic polymers might also be useful in certainapplications; however, if these organic binders are chosen, the additionof a suitable preservative necessary to protect these against biologicaldegradation by molds, rots, rust and the like might also be added.

In any event, a binder, if used, would be chosen to suitably hold thebeforenoted ingredients of my fire retardant material in intimateassociation. The binders noted above, however, except for the solublesilicates, are subject to thermal vaporization or decomposition. Thosebinders which are susceptible to thermal vaporization would, of course,depart upon exposure to combustion temperature. Other if the above notedbinders would leave certain residues behind upon exposure to combustiontemperatures. With the use of certain organic polymers as a binder, athermal decomposition product remains upon exposure of the fireretardant material to combustion temperatures. This product, however,does not inhibit the subsequent reactivity of the heat expandablecomposition and the glass to form the above noted ceramic. Thedecomposition product in fact assists in maintaining the physicalintegrity of my fire retardant material prior to the formation of theceramic product.

If used, the binder should be present in amounts sufficient to impartambient structural integrity of the fire retardant material withoutbeing present in excessive amounts. Amounts from zero percent toapproximately sixty percent of the weight of the unexpanded perlitewould be chosen.

In most instances when used, the binder would only be used on a weightbasis, in amounts equal to or less than the amount of the unexpandedperlite. When urethanes are utilized as the binder and formed in situaround the glass and the unexpanded form of the perlite, application bya spray system is easier if the compounds forming the urethanes arepresent as sixty percent by weight per forty percent by weight of theunexpanded perlite, because of the viscosity of the spray. In situationswhere the viscosity of the compounds being applied is not as critical asin spraying, less binder and mass of the unexpanded form of the perliteis preferred.

For use of ureaformaldehydes, melamine, and soluble alkala metalsilicates, typically forty percent binder would be used. For use withvinyl emulsions, fifteen percent binder would be used and for asphalts,typically fifty percent would be used.

The temperature at which the unexpanded form of the heat expandableperlite starts to expand is as noted above. The particular glass usedwould be chosen such that the glass would not soften to the point beyondthat wherein its viscosity would decrease below the point necessary tomaintain the structural integrity of the material prior to initiation ofexpansion from the unexpanded form to the expanded form of the perlite.In other words, the glass should hold its physical shape until at leastinitiation of expansion has begun. Optimally, the viscosity of the glasswill start decreasing concurrently with or slightly after expansion ofthe heat expandable perlite.

Perlite is mined in a variety of locations throughout the United States.After mining, it is sized and the majority of the larger size particles,normally greater than 50 mesh, are expanded in expansion furnaces attemperatures from about 1500° to 2000° F. This expanded material has avariety of uses including fillers for lightweight aggregates, insulationmaterials and the like. It is also useful neat as an insulating agent,but, of course, it must be confined within some sort of structure.

There is presently little use for the unexpanded perlite left over afterthe above noted processing. This perlite is generally of a size lessthan 50 mesh, and is commonly designated as "cyclone", "00" or "000."With the "00" perlite, the substantial majority of the particles areless than 200 mesh, and with the "000", greater than ninety eightpercent of it is less than 400 mesh. Because it is a by-product of theother useful forms of perlite, but not, in fact, useful in the samequantities as other forms, it is generally just stockpiled at theprocessing site and, in certain instances, forms an extreme disposal orstorage problem for the producing company.

As mined, perlite contains water incorporated into its mineral matrix.When exposed to the above noted expansion temperature, this water isreleased from the matrix and explodes into steam, which expands theunexpanded perlite manyfold times, and concurrently reduces its densitybelow 10 lbs per cu. ft., and in certain instances to as low as 2 lbs.per cu. ft.

I have found that perlite of a mesh size generally less than 100 mesh,will be maintained on or in a permeable glass mass upon expansion fromits unexpanded form to its expanded form. Perlite of a larger size willbe propelled from the glass when it expands and thus is not useful.

The perlite can be successfully permeated into glass fiber mats orfabrics. Further, the unexpanded perlite can also be suspended insolutions of water glasses which are then allowed to dry. Additionally,when utilized with a suitable binder, unexpanded perlite can beassociated with ground glass, microfibers, microspheres and the like.

The perlite can be originally associated with glass using severaltechniques. One technique utilizes a doctor blade to simply spread theperlite over and into a glass mat or fabric. Because of the above notedsize of the unexpanded from of perlite, the fine perlite essentially isforced in or otherwise penetrates into the mat or fabric and isessentially incorporated throughout the total glass matrix. In additionto doctor blading, other "dry" techniques could be used, such as blowingthe perlite into the mat or fabric, using a carrier gas as well asvibrating the glass matrix in the presence of perlite.

"Wet" techniques, wherein perlite is suspended in a suitable liquid,could be used. A suspension of perlite could be poured or sprayed onto asupporting glass matrix, or the matrix could be dipped or otherwise wetwith the perlite suspension.

The perlite also can be incorporated into a suitable binder andtransported into association with the glass concurrently with permeationof a binder into a mass of glass. For example, perlite can be suspendedin heat softened asphalt and transported into association with the glassas the asphalt permeates through the glass mat or fabric. Additionally,it could be suspended in suitable solvent, wherein the binder issoluble, such as a carrier solution for latex. The suspension of perlitein binder solution would then be infiltrated through the glass by eitherpouring or spraying the suspended perlite on the glass, or by dippingthe glass into it.

In other binders, such as those wherein the binder is formed via achemical reaction between two or more components, the perlite could besuspended in one, some, or all of the components and appropriatelypermeated into the glass. In this instance, the binder would be formedin situ within the glass matrix after the perlite had been appropriatelydeposited there by one or more of the binder precursors or carriersolvents.

If the glass is in a form of an unattached mass such as ground glass,microfilaments or microspheres, the perlite could be premixed dry withthe glass and an appropriate binder added to this dry mixture, or thedry mixture added to the appropriate binder. An appropriate dry mixtureof the perlite and an unattached glass mass could be sprayed within thecarrier fluid, either gas or liquid, and a binder concurrently sprayed,such that all of the components were co-deposited on a receptivesurface.

One form of the invention utilizes perlite and an appropriate glassfiber mat held together with asphalt to form a flexible roofing materialwhich can be applied as the outer layer of a roofing structure. A secondform utilizes perlite and a glass fiber mat appropriately bonded as aveneer layer to a building material such as plywood sheet or the like.In this instance, it is envisioned that a separate outer roofingstructure would be applied on top of the above noted laminate.

In any event, the perlite would be present in at least equal weight withthe glass. Preferredly the perlite would be present in amounts greaterthan the weight of the glass. Materials having excellent fire retardantproperties are obtained wherein the perlite is present in weights fromabout 6 or 7 parts-by-weight per one part-by-weight of glass up towherein the perlite present at saturation quantities with respect to theamount of perlite which can be incorporated within a glass fiber mat orfabric. Optimally, around ten parts of greater perlite by weight per onepart glass is presently chosen.

When used with a binder, normally as large a quantity of perlite as canbe incorporated in association with the glass following the aboveguidelines is used, and the binder is present in concentrations withrespect to the perlite as noted above. The optimum amount of binder andperlite on a weight by weight basis is governed by the particular binderselected.

While I do not want to be bound by theory, I believe the excellent fireretardant properties of my fire retardant material are achieved asfollows. Because I utilize the unexpanded form of a heat expandablecomposition, I am able to associate an amount of heat expandable perlitewith a permeable mass of glass such that, after expansion of the heatexpandable perlite, the amount of the perlite present in relationshipwith the glass is such that a ceramic can be formed. When exposed tocombustion after vaporization or decomposition of the binder, if abinder is present, the heat expandable perlite expands to form aninsulation barrier composed of the expanded form of the heat expandableperlite surrounded by glass in a sufficient amount that with furtherincrease in temperature, the expanded form of the perlite and the glassreact to form a ceramic. The physical integrity, i.e., the ability tosupport itself, is transferred from the glass matrix to the ceramic asthe temperature of my material reaches and then surpasses the ceramicforming temperature. Thus, at all times, my fire retardant material canexist as a self supporting material.

As a support of this theory, I prepared a composite of eight layers fora total thickness of 1/4", each layer was composed of 1.9 lbs/100 sq.ft. 20 mil glass mat saturated with perlite using a vinyl latex binder.One side of this composite layer was continuously exposed to 2000° F.flame for one hour. After the one hour exposure, the temperaturemeasured on the cold side was 450° F. On the hot side, the first threelayers had converted to a ceramic with some shrinkage. Adjacent to theceramic layers, the perlite had expanded from its unexpanded form to itsexpanded form, but the glass mat retained its integrity, stillsurrounding the expanded perlite. Progressing beyond toward the coldside, we next see the perlite present in its unexpanded form within theglass fiber mat, followed by, on the cold side, the outer layer being asoriginally formed with the binder still present. A temple stickmeasuring temperatures between 2000° and 2200° F. was used as atemperature indicator on the hot side.

All of the layers of the above composite retained their physicalintegrity, either because of the structural strength of the glass matitself, with or without the binder or conversion to the ceramic. In thistest, individual layers were used. I have also found that in a singlelayer, this same thing happens in essentially a modified scale. In asingle layer, the temperature is slowly increased across the thicknessof the fire retardant material. The hot side is first to have itsperlite expand and first to have the ceramic form. Expansion of theperlite and the formation of the ceramic proceeds as a gradient throughthe thickness of the material. The binder, if it is used, of coursewould likewise be present or absent in a gradient as the temperatureincreases across the thickness of the material. In a single layer thefiber mat with or without binder and/or another form of the glass with abinder would maintain the integrity of the structure at the cold side asthe hot side converted to a ceramic and then the ceramic on the hot sidewould retain the integrity of the structure as the ingredients, whichare more distant from the source of the heat, underwent expansion andglass softening and, finally, conversion to ceramic.

Typical examples of use of my invention are as follows. A solution ofsodium silicate was mixed with the unexpanded form of the expandableperlite in a mesh size consistent with the invention. The resultingsuspension was spread across the surface of a cardboard sheet. After aminimal drying time, the flame from a propane torch was directed againstthe resulting fire retardant material. After fifteen minutes of suchtreatment, a ceramic had formed where the flame had impinged, butdirectly behind it, the cardboard still had not been charred or burned.

A glass mat was impregnated with the perlite of the invention by simplyrubbing the perlite into the mat. Upon exposure to a flame, a circulararea of ceramic formation was noted, with no flame penetration throughthe mat. When the mat was treated with a flame without the addition ofthe perlite, a hole quickly formed where the flame impinged on the mat.

A flexible roofing composition was prepared by admixing 6.2 lbs. ofperlite with 6.2 lbs. of heat softened asphalt and spreading over andthrough a glass fiber mat having a density of 1.9 lbs./100 sq. ft. Theresulting composition had a total weight of 14.29 lbs./100 sq. ft. Whensubjected to combustion by impinging a torch against the surface,initially decomposition of the asphalt was noted followed by charringand then formation of a ceramic. A typical test piece held in a flamefor fifteen minutes had a small gray-white colored circle ofapproximately 3 to 4 inches in width at the point of flame impingement.In this circle the asphalt had decomposed and the very center of thecircle had converted to a ceramic. Outside the circle the original blackcomposition showed no effects of being adjacent to the flame test area.

Another typical roofing material utilized the same glass mat notedabove, known in the industry as E-grade industrial mat, with 11.34 lbs.of asphalt and 11.34 lbs. of perlite per sq. ft. Flame tests of thismaterial showed results consistent with flame tests of the abovematerial. Both of the above noted roofing materials had excellent flameretardant properties.

As a composition suitable for veneering into a laminate such aspressboard, fiberboard, plywood or the like, 15 parts perlite weresuspended in 10 parts water and 5 parts latex acrylic copolymermaterial. Optionally, 0.5 parts suspending agent could also be utilized.This material was saturated into the 1.9 lbs./100 sq. ft. glass mat,which was pre-positioned on the surface of a piece of 1/2" plywood.Three layers were built up in this manner. The resulting structure was aplywood veneered with a fire retardant material.

The following structures were prepared and subjected to analagousconditions utilized in the Fire Brand B test of UL 790 testingprocedures. All of the following met or exceeded these conditions.

Perlite suspended in a vinyl latex carrier was painted onto a rigidurethane foam. Glass fibers were compressed into the layer. A secondperlite vinyl latex layer was painted on and again glass fibers werepressed into it. This was repeated for a third time, resulting in alayer of approximately 1/8" thick. As noted above, it successfullywithstood conditions analagous to the Class B portin of the above notedtest.

The above test was repeated utilizing a latex carrier--perlite ratio of75 percent perlite to 25 percent latex carrier. A composite structure1/8" thick, utilizing 3 layers of 1.5 lb/100 sq. ft. glass mat wasformed. After having a propane torch flame impinged in it for one hour,only slight charring of the urethane was noted.

Three layers of a 50/50 perlite/warm asphalt suspension impregnated intoa glass mat were used as an under-layment for a pressure treated shakeshingle structure. This structure also passed a test analagous to theClass B Fire Brand. In a separate test, the above noted shake shingleswere also utilized over space sheeting. Again, the material successfullypassed the noted test. Presently, the only known existing pressuretreated shingle which can successfully pass this same test is thatbacked up with steel foil on solid sheeting.

A composition of approximately 150 mil thickness was formed by layeringa urethane elastomer with glass impregnated perlite suspended in a waterbased vinyl emulsion, followed by a second layer of glass, perlite,etc., and a final layer of urethane elastomer. This was applied to a1/2" plywood decking. Approximately 90 mils of 150 mil thickness werethe perlite-glass-vinyl emulsion layers. This layer also withstoodconditions analagous to the above noted test.

The ceramic resulting from high heat exposure of the fire retardantmaterial of my invention shows on microscopic inspection to be a ceramicof many closed cells. The presence of these closed cells impart to thisceramic additional heat insulating properties at extremely hightemperatures.

The sodium silicates useful as the permeable mass of glass of myinvention can be utilized as water solutions or as dehydrated, orpartially dehydrated, solids. Both of these physical forms arecommercially available. If used in a solid form, the sodium silicatescould be appropriately dry mixed with the perlite and the resultingmixture then used in a manner consistent with other solid forms of glassdescribed herein. Alternatively, such a dry mixture might then beadmixed with water and used. When used as a solution, sodium silicatecould be mixed directly with the perlite or it could be step-wise orconcurrently applied to a surface with the perlite.

My fire retardant material as described herein utilizes the insulatedproperties of the expanded form of the heat expandable perlite after theexpansion temperature has been surpassed. In certain instances, it mightbe desirable to incorporate a previously expanded insulation material toprovide for low temperature insulating properties. In certain structuralsteel structures, it is desirable to protect the structural steel fromexposure to temperatures in the range of about 500° F. and above. Aminor fire in one of these steel structures might not do catastrophicdamage to the whole structure, but it might locally expose certainstructural steel elements to temperatures of about 500° to 700° F. Thesetemperatures could initiate softening of tempered steel components andthus are undesirable. This normally is below the temperatures at whichthe heat expandable perlite of my invention would expand into a highlyinsulative expanded form. By incorporating amounts of previouslyexpanded insulatory material such as expanded perlite, or otherinsulatory materials into my fire retardant material, structural steelcomponents as well as other structural materials coated with such amaterial would be protected against low temperatures as well as hightemperature exposures.

I claim:
 1. A process of rendering a material fire retardant whichcomprises:overlaying said material with at least one layer of apermeable mass of silica glass; permeating among and associating withinsaid permeable mass of silica glass a quantity of the unexpanded form ofheat expandable perlite wherein said perlite is present as particles ofa mesh size less than 100 mesh and said quantity of perlite is aquantity at least equal to the weight of said permeable mass of saidsilica glass.
 2. The process of claim 1 wherein:said perlite is of aparticle size smaller than about 200 mesh.
 3. The process of claim 1including:adhereing said perlite to said permeable mass of silica glasswith a binding agent capable of maintaining said perlite in saidassociation with said silica glass.
 4. The process of claim 3 whichcomprises:overlaying said material with a first layer of a permable massof a silica glass; permeating among and associating with said firstlayer of silica glass a quantity of said unexpanded form of said heatexpandable perlite; adhering said perlite to said first layer of silicaglass with a binding agent capable of maintaining said perlite inassociation with said silica glass; adhering at least a second layer ofa permeable mass of silica glass to said first layer with said bindingagent; permeating among and associating with said second layer of saidglass a quantity of said unexpanded form of said heat expandableperlite; adhering said perlite to said second layer of glass with saidbinding agent.
 5. The process of claim 4 wherein:said permeable mass ofsilica glass is chosen from the group consisting of glass fiber mats,glass fiber fabric and glass fiber filaments.
 6. The process of claim 5wherein:said silica glass is a soda-lime-silica glass.